Adaptability of RMR for marine gas hydrate drilling

Abstract:

Natural gas hydrate(NGH) sedimentary bodies are shallow, soft and unconsolidated, where the mud window is narrow. It is time-consuming and expensive to drilling NGH with conventional riser drilling; meanwhile, NGH dissociation leads to changes in NGH saturation and wellbore pore pressure, causing the mud window to narrow down and the borehole be instability. This paper introduces the principle of deep water riserless mud recovery drilling (RMR) and analyzes its adaptability in marine NGH drilling. The results indicate that RMR can solve the problem of the narrow mud window. The real-time monitoring system can improve the maneuverability and completely eradicate the hydrothion leakage. It simplifies the wellbore configuration and reduces the well construction cost. It is safe and environment friendly without any discharge into the ocean.

Key words:marine drilling; marine natural gas hydrate; reserless mud recovery drilling (RMR); dual gradient drilling; risk of drilling